The U.S. ambassador to the United Nations will travel to the heavily armed North Korean border and meet defectors in South Korea, his office said on Monday, as U.N. efforts to secure sanctions against North Korea falter.

Ambassador Linda Thomas-Greenfield is scheduled to travel from April 14 to 20 after Russia rejected an annual update from a multinational panel of experts that has spent the past 15 years enforcing U.N. sanctions aimed at curbing North Korea’s nuclear and missile weapons program.

Washington, Seoul and Tokyo criticized Moscow’s veto and China’s abstention, which experts said would undermine sanctions enforcement, with one South Korean envoy likening it to “destroying CCTV to avoid being caught red-handed.”

Nate Evans, spokesman for the U.S. mission to the United Nations, said Thomas-Greenfield’s trip will also stop in Japan and is aimed at promoting bilateral and trilateral cooperation on sanctions and other aspects.

South Korea and Japan are currently members of the Security Council.

“Ambassador Thomas-Greenfield will discuss next steps in both countries to ensure continued independent and accurate reporting on North Korea’s ongoing weapons proliferation and sanctions evasion activities,” Evans said in a statement, referring to the North Korea’s official name is “North Korea”. Democratic People’s Republic of Korea.

In South Korea, Thomas Greenfield will travel to the heavily fortified demilitarized zone between North and South Korea to meet with young defectors and students at Ewha Womans University, Evans said.

In Japan, she will also meet with the families of Japanese citizens abducted by North Korea in the early 2000s and visit Nagasaki, which suffered a U.S. nuclear bombing in 1945.